1. Field of the Invention
This invention relates to a respiration-synchronized oxygen supplying apparatus detecting respiration of a human being by means of a sensor thereof and supplying oxygen in synchrony with timings of inhale. More particularly, this invention relates to an oxygen supplying apparatus capable of suppressing oxygen loss down to a lower level with a simple structure without use of a three-way valve.
2. Description of Prior Art
Recently, in a site of medical treatment in a home or in emergency, a combination of an oxygen cylinder and an oxygen supplier easily provides medical treatments which supplies oxygen. Since an oxygen cylinder used for such a purpose is made compact in consideration of portability or the like, it is a concern how to reduce oxygen consumption. For this reason, respiration-synchronized oxygen supply apparatuses which supply oxygen at proper timing in an appropriate amount in synchrony with respiration are now becoming majority.
As such a respiration-synchronized oxygen supplying apparatus, for example, an oxygen supplying apparatus shown in FIG. 6 has been proposed. The oxygen supplying apparatus 51 includes a negative pressure sensor 52, a three-way valve 53 having a first port 53a, a second port 53b, and a third port 53c, and a controller 54 for switching the three-way valve 53 based on information from the negative pressure sensor 52.
A cannula, not shown, is coupled to the first port 53a of the three-way valve 53 and connected to a human being (body of human being) P, while an oxygen cylinder, not shown, is coupled to the second port 53b as for oxygen supplier G. The third port 53c is connected to the negative pressure sensor 52.
In this system, the three-way valve 53 communicates the first and third ports with each other at a standby stage, thereby communicating the human being P and the negative pressure sensor 52 with each other. When the human being makes respiration in this situation, the negative pressure sensor 52 detects inhale of human being and reports it to the controller 54. The controller 54, in response to this, immediately switches the three-way valve 53 as to communicate the first and second ports 53a, 53b with each other, thereby supplying oxygen from the oxygen supplier G to the human being P.
The controller 54, after passing a certain period, makes the three-way valve 53 back to a state that the first and third ports 53a, 53c are in communication with each other, or namely a standby state, and repeats the above control upon detection of inhales of the human being.
According to such a conventional apparatus, supply of oxygen in proper synchrony with inhaling timing in respiration of human being can suppress oxygen consumption of the oxygen supplier G and extend time for use. In addition to this advantageous point, because the three-way valve 53 cuts off the communication between the oxygen supplier G and the negative pressure 52 while oxygen is supplied, the valve can prevent the oxygen to be supplied from escaping toward the negative pressure sensor 52, suppress unnecessary oxygen consumption, allow the user to effectively use the oxygen in a limited amount contained in the compact oxygen cylinder.
It is to be noted that the respiration-synchronized oxygen supplying apparatus described above is specifically disclosed in Japanese Patent Publication (KOKOKU) Heisei 4-3,229.
With the above conventional apparatus, however, there was a problem that the apparatus lacks good durability because the three-way valve switches with high frequency between a state coupling between the first and third ports 53a, 53c (the standby state) and the other state coupling between the first and second ports 53a, 53b (the oxygen supply state).
To solve this problem, a simplified structure in which the negative pressure sensor 52 is made in direct communication with the human being P and which a two-way valve is provided to simply open and close a passage between the oxygen supplier G and the human being P may be conceivable, but with this structure, oxygen normally leaks toward the negative sensor 52 while oxygen is supplied, thereby raising again a fundamental problem that time for use is shortened where the oxygen amount is limited.
It is an object to provide an oxygen supplying apparatus having an improved durability with a simply structured valve capable of preventing oxygen from leaking toward a negative pressure sensor even while oxygen is supplied.
The foregoing object is accomplished by a respiration-synchronized oxygen supplying apparatus according to the invention which includes a sensor detecting inhale of respiration of a human being; a valve installed between a first gas passage coupled with the human being and a second gas passage coupled with an oxygen supplier; a controller for controlling the valve based on information from the sensor; a negative pressure generating mechanism having a gas communication area that becomes larger as comes closer to the side of the human being from the side the oxygen supplier; and a third gas passage provided with the negative pressure generating mechanism for normally communicating the sensor with the human being.
According to an embodiment of the invention, in a respiration-synchronized oxygen supplying apparatus, the sensor includes a casing having first and second passage holes, and a planer piezoelectric device contained in the casing whose plane faces to the first passage hole and does not face to the second passage hole, where the second passage hole of the sensor is coupled to the third gas passage. With this structure, the oxygen supplying apparatus can possess good durability without receiving loads of positive pressure due to exhale of respiration.